Newsgroups: comp.robotics
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From: WELLS <WELLS@CTSD2.JSC.NASA.GOV>
Subject: Re: Solid State Cooling
Message-ID: <1993Feb26.141543.4845@aio.jsc.nasa.gov>
X-Xxdate: Fri, 26 Feb 93 14:16:26 GMT
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References: <1993Feb24.145131.17526@bcrka451.bnr.ca> <laird.730597442@pasture.ecn.purdue.edu> <1993Feb25.010541.29344@netcom.com>
Date: Fri, 26 Feb 1993 14:15:43 GMT
Lines: 50

In article <1993Feb24.145131.17526@bcrka451.bnr.ca> Glen Sandness, 
sandness@bnr.ca writes:
>
>I have a small computer in a sealed metal case, and I'd like to use one 
of these things for managing heat buildup inside the case.  For 
condensation reasons, I'd rather not just drill ventilation holes and 
install a fan.
>...
>Can anyone suggest other approaches to this problem?

ALSO
In article <1993Feb25.010541.29344@netcom.com> Mark W. Moorcroft, 
sevenup@netcom.com writes:
>There is a company that makes a computer cooled by a fluid filled
>plastic bag draped over the circuit board to provide a heat path to
>the outside of the case. It sounds risky but it really looks like an


You might try a very simple heat pipe similar to the method Mark 
outlined. It is a way to get heat away from small isolated sources 
inside a container to or thru its walls. I have a Denon stereo receiver 
that uses one to carry heat away from a densely populated amplifier 
section to a conventional heat sink located in an off board area. It is 
very simple. This particular receiver is at least 8 years old and runs 
very cool. IF you can keep the unit relatively  horizontal, this is by 
far better than other methods. Also if the unit will undergo constant 
agitation this will work even better(like sodium filled exhaust valves 
in aircraft and some Volkswagen engines). If it cant be kept horizontal, 
or constantly agitated, try carrying heat to the outside wall using 
copper strap or copper sheet or even thick copper foil. Peltier units 
are best described as self-eating-watermelons. The I2R losses and 
internal heat transfer in them unavoidably use up much of their cooling 
capacity.

If you elect to make a heat pipe, the trick is to purge or otherwise 
remove the air from the tube and seal it with only the liquid and its 
vapor remaining in the tube. Copper tube is also best. Its length has 
little to do with its heat transfer capacity. Its only requirement is 
that the liquid and vapor both be able to freely communicate (flow) 
between the heat input and output areas. 


                                                    HEAT OUT
     ______________________________________________________________
    /                                                              \
   |                     VAPOR                                     |
   |---------------------------------------------------------------|
    \______________________LIQUID__________________________________/

         HEAT IN
